There was a great intro to the US newsletter that I wanted to share:

Microsoft recently updated its software licensing terms for 41 server applications, and updated its technical support policy for 31 server applications so that customers can receive technical support when deploying those applications on Windows Server 2008 Hyper-V, Microsoft Hyper-V Server, or any validated third-party virtualization platform.
With the new licensing terms, Microsoft is waiving its previous 90-day reassignment rule, allowing customers to reassign licenses from one server to another within a server farm as frequently as needed. For scenarios around how the licensing terms might work for you, check out the Virtualization Team blog.
With the new support policies, customers get the same level of product support in a virtualized environment that they are accustomed to with non-virtual environments. To enable this support policy, Microsoft launched the Server Virtualization Validation Program in June 2008. The program is open to any software vendor to test and validate its virtualization software to run Windows Server 2008 and previous versions of Windows Server. More information is available on the Microsoft Support Web site.